2 c. brown sugar, firmly packed
1/2 c. butter
1/2 c. evaporated milk
1 tsp. vanilla

Cream brown sugar, butter and milk in saucepan. Place over heat, stirring until sugar is dissolved; then boil without stirring for 5 minutes until mixture forms a soft ball. Remove from heat. Beat until the mixture is cold and thickened. Beat in vanilla. Spread on cake.